Did you ever try to levitate a magnet with the help of bunch of other magnets? It seems very easy: since magnets can repel each other you probably can put a bunch of magnets in circle so they equally push the other magnet towards the center of the system. Or maybe even build a sphere made of magnets that would suspend another magnet in the center. But if that’s so easy why it is so difficult to build trains that use magnetic levitation? If you try these “easy” methods you will find they all do not work. In fact back in 1842 British mathematician Samuel Earnshaw proved that it is in fact impossible to suspend a regular magnet in space with the sole help of other regular magnets statically placed around it. Well he didn’t prove exactly that, but this follows from his original theorem. The proof of the theorem contains too many Greek letters to explain it in this short video, so let’s just trust those smart guys who triple checked it and found it correct.

So it is impossible to suspend a magnet in space using just bunch of other magnets. But take a look at the video. There is a large ring ceramic magnet and another magnet which is also a top. And if I carefully spin the second magnet above the first one it will indeed hand in the air. How is that possible?! Let’s talk about this and a few other loopholes in the Earnshaw’s Theorem and actually build a few magnetic levitation devices. This is gonna be cool!continue reading "RTFMs Episode #8: How to Build a Magnetic Levitating Top"